1. Field of the Invention
This invention generally relates to laser eye surgery, and in particular, provides methods, devices, and systems for selectively ablating corneal tissue to improve the vision of patients having corneal irregularities.
Laser eye surgery systems and methods are now used to correct defects in vision using a technique known as ablative photodecomposition. In general, these techniques selectively expose the cornea to laser radiation so as to selectively remove and resculpt the cornea and achieve a desired change in shape of the cornea to treat an optical defect.
Laser eye surgery is now being used to treat a variety of vision defects, including myopia (nearsightedness), hyperopia (farsightedness), and symmetrical cylindrical astigmatisms. To achieve these results, known laser eye surgery systems make use of a variety of mechanisms to selectively expose the corneal tissue to the ablative laser energy so as to change the optical characteristics of the eye uniformly throughout the optically used portion of the cornea. Often times, the desired change in shape is effected by selectively removing corneal tissue according to a spherical ablation profile (for example, for treatment of myopia and hyperopia). Cylindrical astigmatism is often treated by selectively removing corneal tissue according to a cylindrical profile, in which the cylinder extends laterally across the optical axis of the eye.
Many patients suffer from optical defects which are not easily treated using known spherical or cylindrical ablation techniques. It has been proposed to treat patients suffering from nonsymmetrical or other types of astigmatism by defining a custom ablation profile. Ophthalmic measurement techniques which may be capable of generating highly accurate topographic information on a particular cornea are now being developed. Unfortunately, integrating these topographic measurements together with new ablation algorithms may take years. In the meantime, patients having irregular corneal defects which significantly limit their vision are in need of treatment today.
In light of the above, it would be desirable to provide improved laser eye surgery devices, systems, and methods. It would be beneficial if these improvements allowed the treatment of irregular corneal defects, particularly if these benefits were available and safe for use in the near-term.
2. Description of the Background Art
The following patents and patent applications may be relevant to the present invention: U.S. Pat. No. 5,683,379, issued Nov. 4, 1997, for "Apparatus for Modifying the Surface of the Eye Through Large Beam Laser Polishing and Method of Controlling the Apparatus", U.S. Pat. No. 4,724,522, issued Feb. 9, 1988, for "Method and Apparatus for Modification of Corneal Refractive Properties", U.S. Pat. No. 5,098,426, issued Mar. 24, 1992, for "Method and Apparatus for Precision Laser Surgery", U.S. Pat. No. 5,290,272, issued Mar. 1, 1994, for "Method for the Joining of Ocular Tissues Using Laser Light", U.S. Pat. No. 5,314,422, issued May 24, 1994, for "Equipment for the Correction of Presbyopia by Remodelling the Corneal Surface by Means of Photo-Ablation", U.S. Pat. No. 5,391,165, issued Feb. 21, 1995, for "System for Scanning a Surgical Laser Beam", U.S. Pat. No. 5,439,462, issued Aug. 8, 1995, for "Apparatus for Removing Cataractous Material", U.S. Pat. No. 5,549,596, issued Aug. 27, 1996, for "Selective Laser Targeting of Pigmented Ocular Cells", U.S. Pat. No. 5,549,597, issued Aug. 27, 1996, for "In Situ Astigmatism Axis Alignment", U.S. Pat. No. 5,556,395, issued Sep. 17, 1996, for "Method and System for Laser Treatment of Refractive Error Using an Offset Image of a Rotatable Mask", U.S. Pat. No. 5,634,919, issued Jun. 3, 1997, for "Correction of Strabismus by Laser-Sculpting of the Cornea", U.S. Pat. No. 5,637,109, issued Jun. 10, 1997, for "Apparatus for Operation on a Cornea Using Laser-Beam", PCT International Application No. PCT/EP95/01287, filed Apr. 7, 1995, for "Method and Apparatus for Providing Precise Location of Points on the Eye", European Patent Application No. 94303256.5, filed May 5, 1994, for "Method and System for Laser Treatment of Refractive Errors Using Offset Imaging", U.S. patent application Ser. No. 09/274,499, filed Mar. 23, 1999, for "Multiple Beam Laser Sculpting System and Method". The full disclosure of these references is hereby incorporated by reference.